• Applied Chemistry for Engineering
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• v.7 no.3
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• pp.543-553
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• 1996

Oxygen reduction in an alkaline fuel cell was studied by using perovskite type oxides as an oxygen electrode catalyst. The high surface area catalysts were prepared by malic acid method and had a formula of $La_{0.6}Sr_{0.4}Co_{1-x}Fe_xO_3$(x=0.00, 0.01, 0.10, 0.20, 0.35 and 0.50). From the result of XRD pattern and specific surface area due to the amount of Fe substitution and the consumption of ammonia-water, the complex formation of Fe ion with $NH_3$ was the main factor for both the phase stability of perovskite and the increase of specific surface area. Multi-step calcination was necessary to give a single phase of perovskite in catalyst precursor. The crystal structure of the catalysts was simple cubic perovskite, which was verified from the XRD patterns of the catalysts. The activity of oxygen reduction was monitored by the techniques of cyclic voltammetry, static voltage-current method, and current interruption method. The activity(current density) of oxygen reduction showed its minimum at x=0.01 and its maximum between 0.20 and 0.35 of x-value in $La_{0.6}Sr_{0.4}Co_{1-x}Fe_xO_3$. This tendency was independent of the change of surface area.

• Applied Chemistry for Engineering
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• v.7 no.3
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• pp.496-503
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• 1996

Aromatic and aliphatic copolyesters for the dispersing agent were synthesized by two stage reaction, esterification and polycondensation. Copolyesters were blended with PET in the melt state and their thermal and rheological properties were investigated. From GPC analysis Mn's and Mw's of copolyesters were about 30000 and 65000g/mol, respectively. From DSC experiment copolyesters had melting range of $90{\sim}150^{\circ}C$. Copolymer composition was in good agreement with comonomer feed ratio from $^1H$-NMR analysis. Copolyesters and SPA (standard sample) were blended with PET in the melt state. From DSC experiment, copolyesters and SPA were miscible with PET. From the dynamic melt viscosity experiment, melt viscosity of blended sample was increased as the content of aromatic copolyester was increased, while it was decreased as the content of aliphatic and SPA were increased. As for volume resistivity of dry color containing carbon black and copolyesters with dispersing time, aromatic copolyester showed highest value. It was conferred from this result that aromatic copolyester was the best dispersing agent for carbon black in PET resin.

• Applied Chemistry for Engineering
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• v.5 no.4
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• pp.698-705
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• 1994

The basic medium oil modified alkyd resin was synthesized from linseed oil fatty acid(LOFA), phthalic anhydride(PAA), maleic anhydride(MA) and trimethylol propane(TMP) by condensation polymerization at $230^{\circ}C$. MA/TMPTA modified water-reducible alkyd resins were synthesized with TMPTA graft copolymerization onto the basic resin at $180^{\circ}C$. Acid value of the resin was controlled by the addition amount of MA and N,N-dimethylethanol amine(DMEA) was used as a neutralizing agent to prepare of the water-reducible alkyd resin. The effect of TMPTA on the graft copolymerization of the resin was studied by measuring molecular weight glass transition temperature(Tg), viscosity, graft efficiency, and gel contents of melanin cured film. Heat resistance, UV resistance and water resistance of cured film of MA/TMPTA modified resin was compared to those of TMA/TMPTA modified alkyd resin. The molecular weight, viscosity gel contents and graft efficiency of water reducible alkyd resin were increased according to the TMPTA graft copolymerization, but Tg was decreased. The viscosity was lower when the solid contents reached 40% than that of 30% content and also and also became lower with the extent of neutralization ratio, The heat resistance, UV resistance and water resistance of the MA/TMPTA modified alkyd resis were better than those of TMA/TMPTA modified alkyd resin but the storage stability of the TMA/TMPTA alkyd resis was better than that of MA/TMPTA modified alkyd resin.

• Applied Chemistry for Engineering
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• v.5 no.4
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• pp.616-623
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• 1994

Conductive Polypyrrole films have been synthesized by electrochemical method in nucleophilic solvent such as N, N-dimetylformamide(DMF), dimethylsulfoxide(DMSO). The effect of protic acid as supporting electrolyte to decrease the nucleophilicity of the solvent was studied. Cyclic voltammetry, I-t transients were carried out to investigate the electrodeposition of conductive polypyrrole film on platinum electrode. Three peaks of 0.65V, 0.85V, and 1.2V vs. $Ag/AgNO_3$ indicated oxidation of monomer, oxidation of pyrrole to the platinum electrode and decomposition of polypyrrole film, respectively. With the I-t transients, nucleation process was confirmed and from obtained linear fits of I vs.t2resembles the metal film formation, and 2.15-2.26 of n-value could be calculated. As concentration of pyrrole or prolic acid was increased, the conductivity of polypyrrole film increased linearly. Tensile strength and elongation were investigated for comparing the mechanical properties and also SEM was performed for morphology investigation.

• Applied Chemistry for Engineering
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• v.5 no.4
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• pp.597-608
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• 1994

A new process for the production of high purity ${\alpha}-Al_2O_3$ from ammonium aluminium sulfate solution abtained through the sulfation of low grade bauxite ore with $(NH_4)_2SO_4$, and leaching of the sulfated product was investigated. This process is consisted of solvent extraction for Fe component removal from ammonium aluminum sulfate solution and homogeneous precipitation of Al containing precipitate from the refined ammonium aluminium sulfate solution by using urea as precipitator. The optimum conditions of solvent extraction with Alamine 336 as extractant were shaking time of 4min, organic phase ratio to aqueous phase of 0.25. The types of precipitation products from this precipitation were amorphous alumina gel, pseudo-boehmite and crystalline boehmite in the lower temperature of $100^{\circ}C$, in the range from $125^{\circ}C$ to $150^{\circ}C$, and above $150^{\circ}C$, respectively. And also amorphous alumina gel hydrate in $1000^{\circ}C$ and crystalline boehmite in $1250^{\circ}C$ were tranfered to ${\alpha}-Al_2O_3$, respectively. This alumina was identified as ${\alpha}-Al_2O_3$ of purity 99.7%.

• Applied Chemistry for Engineering
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• v.5 no.4
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• pp.588-596
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• 1994

A decomposition reaction of bauxite ore with $(NH_4)_2SO_4$ was investigated to prepare Al component pregnant solution for the direct product of high purity $Al_2O_3$ from low grade bauxite ore. Al component in the bauxite was sulfatized to $NH_4Al(SO_4)_2$ or $Al_2(SO_4)_3$ in this decomposition. The optimum conditions of the decomposition for bauxite ore were reaction temperature of $425^{\circ}C$, reaction time of 40min, $(NH_4)_2SO_4$ weight ratio to bauxite of 7.0 and particle size of bauxite ore of -200mesh. The optimum leaching conditions of sulfated bauxite ore were leaching temperature of $100^{\circ}C$, leaching time of 1hr and pulp density of 200ml $H_2O$ to sulfated ore of 1.0g bauxite. Under the above mentioned decomposition and leaching conditions, 94% of Al component in the bauxite ore was extracted.

• Korean Journal of Clinical Laboratory Science
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• v.52 no.1
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• pp.69-77
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• 2020

The tumor suppressor gene, p53, is inactivated in the human hepatocellular carcinoma cells line, Hep3B. Berberine has been reported to inhibit the proliferation of cancer cells. This study examined whether apoptosis was induced in berberine-treated Hep3B cells and observed the association between apoptosis and the expression of p53 and DNA methyltransferase (DNMT). The cell viability was measured using an MTT assay. Apoptosis of Hep3B was measured using annexin V flow cytometry. Berberine-treated cells were examined for their DNMT enzymatic activity, mRNA expression, and protein synthesis. The p53 levels were examined by Western blot analysis. The berberine treatment resulted in increased Hep3B cell death and apoptosis in a time- and dose-dependent manner. The DNMT3b activity, mRNA expression, and protein levels all decreased after the berberine treatment. In contrast, the p53 protein levels increased with a concomitant decrease in DNMT3b. No change in the expression of ERK was observed, but the P-ERK levels decreased in a dose dependent manner. These results indicate that a treatment of Hep3B cells with berberine can reduce the expression of DNMT3b, leading to an increase in the tumor suppressant gene p53 and an increase in cell apoptosis. This shows that berberine can effectively suppress the proliferation of liver cancer cells.

• Journal of Embryo Transfer
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• v.27 no.4
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• pp.245-252
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• 2012

The purpose of the present study was to investigate the effect of IFN-${\tau}$ on prostaglandin synthesis, cyclooxygenase-2 (COX-2) gene expression in vitro and concentration of progesterone (P4) in endometrial cells. Epithelial and stromal cells cultured in vitro were isolated from bovine endometrium and stimulated with increasing doses of IFN-${\tau}$ (0, 0.02, 0.2 and 2 ug/ml). Human chorionic gonadotropin (hCG, 1.5 IU/ml) was used as a positive control. Prostaglandin $E_2$ and $F_{2{\alpha}}$ levels in the culture media were analyzed by enzyme immunoassays and total RNA was extracted from the cells for RT-PCR. P4 concentrations of blood samples were assayed by chemiluminescent immuno assays system. In epithelial cells, COX-2 gene expression was increased in the presence of IFN-${\tau}$ (p<0.05), but it was not significantly different in all groups of stromal cells except for 2 ug/ml IFN-${\tau}$ group (p<0.05). Although IFN-${\tau}$ did not affect $PGE_2$ and $PGF_{2{\alpha}}$ production in epithelial cells, it decreased $PGE_2$ and $PGF_{2{\alpha}}$ production significantly in stromal cells (p<0.05). In vivo experiment, blood concentration of P4 was significantly increased after addition of IFN-${\tau}$ (1 ug/ml). The results indicate that PG production was mediated by COX-2 expression in stromal cells but it was not affected in epithelial cells and this suggest that treatment of IFN-${\tau}$ could improve the implantation environment of uterine by maintenance of high P4 concentration.

• Journal of Life Science
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• v.14 no.2
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• pp.325-330
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• 2004

The RAD3 gene of Saccharomyces cerevisiae is required for excision repair and is essential for cell viability. RAD3 encoded protein possesses a single stranded DNA-dependent ATPase and DNA and DNA-RNA helicase activities. To examine the extent of conservation of structure and function of RAD3 during eukaryotic evolution, the RAD3 homolog gene was isolated by screening of genomic DNA library. The isolated gene was designated as HRD3 (Homologue of RAD3 gene). The over-expressed HRD3 protein was estimated to be a 75 kDa in size which is in good agreement with the estimated by the nucleotide sequence of the cloned gene. Two-dimensional gel electrophoresis showed that a number of other protein spots dramatically disappeared when the HRD3 protein was overexpressed. The overexpressed RAD3 protein showed a toxicity in E. coli host, suggesting that this protein may be involved in the inhibition of protein synthesis and/or degradation of host protein. To determine which part of HRD3 gene contributes to the toxicity in E. coli, various fusion plasmids containing a partial sequence of HRD3 and lac'Z gene were constructed. These results suggest that the C-terminal domain of HRD3 protein may be important for both toxic effect in E. coli and for its role in DNA repair in S. pombe.

• Journal of Life Science
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• v.6 no.3
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• pp.185-192
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• 1996

Bacteriophage T7 gene 2.5 protein, a single-stranded DNA binding protein, is required for T7 DNA replication, recombination, and repair. T7 gene 2.5 protein has two distinctive domains, DNA binding and C-terminal domain, directly involved in protein-protein interaction. Gene 2.5 protein participates in the DNA replication of Bacteriophage T7, which makes this protein essential for the T7 growth and DNA replication. What gene 2.5 protein makes important at T7 growth and DNA replication is its binding affinity to single-stranded DNA and the protein-protein important at T7 DNA replication proteins which are essential for the T7 DNA synthesis. We have constructed pGST2.5(WT) encoding the wild-type gene 2.5 protein and pGST2.5$\Delta $21C lacking C-terminal 21 amino acid residues. The purified GST-fusion proteins, GST2.5(WT) and GST2.5(WT)$\Delta$21C, were used for whether the carboxyl-terminal domain participates in the protein-protein interactions or not. GST2.5(WT) and GST2.5$\Delta$21C showed the difference in the protein-protein interaction. GST2.5(WT) interacted with T7 DNA polymerase and gene 4 protein, but GST2.5$\Delta$21C did not interact with either protein. Secondly, GST2.5(WT) interacts with gene 4 proteins (helicase/primase) but not GST2.5$\Delta$21C. these results proved the involvement of the carboxyl-terminal domain of gene 2.5 protein in the protein-protein interaction. We clearly conclude that carboxy-terminal domain of gene 2.5 protein is firmly involved in protein-protein interactions in T7 replication proteins.